WO2000045418A1

WO2000045418A1 - Electrode for discharge tube and discharge tube using it

Info

Publication number: WO2000045418A1
Application number: PCT/JP2000/000383
Authority: WO
Inventors: Nobuharu Harada; Syoji Ishihara
Original assignee: Hamamatsu Photonics K.K.
Priority date: 1999-01-26
Filing date: 2000-01-26
Publication date: 2000-08-03
Also published as: DE60044667D1; US20010052755A1; AU2318800A; EP1150335B1; EP1150335A1; US6664733B2; JP3337658B2; EP1150335A4; JP2000215845A

Abstract

A discharge tube (10) comprising a glass bulb (12), a cathode (14) and an anode (16), wherein the cathode (14) comprises a cathode tip end (22) and a lead bar (24). The lead bar (24) has a cylindrical shape formed of Mo and is formed at one end face (24a) thereof with a cylindrical projection (24b). The cathode tip end (22) is formed by impregnating Ba into porous tungsten, and has a conical steeple (22a) at one end side facing the anode (16) and a cylindrical insertion hole (22d) for receiving the projection (24b) of the lead bar (24) at an end face (22c) on the other end side thereof. A gap between the end face (24a) of the lead bar (24) and the end face (22c) of the cathode tip end (22) is filled with an Mo-Ru brazing filler metal (26).

Description

Say 糸

Electrode for discharge tube and discharge tube using the same

The present invention relates to a discharge tube electrode and a discharge tube using the same. Background art

Discharge tubes are widely used as light sources for lighting and measuring instruments. The discharge tube is a light source that emits light by causing a cathode and an anode to face each other and sealed in a discharge gas atmosphere, and causing an arc discharge between the cathode and the anode. Such a discharge tube is provided with electrodes as disclosed in, for example, Japanese Utility Model Publication No. 4-33888. In other words, it is an electrode in which a cap-shaped impregnated electrode made by impregnating a porous high-melting-point metal with an electron-emitting material is covered on the tip of a high-melting-point metal rod. By using an electrode in which a porous high-melting-point metal is impregnated with an electron-emitting material, as in the above-described electrode, electron emission can be easily obtained and damage to the tip of the electrode is reduced. Disclosure of the invention

However, the discharge tube, particularly the electrode used for the discharge tube, has the following problems. That is, since the above-mentioned electrode uses a rod-shaped member, that is, a high melting point metal rod as a base portion of the electrode, the contact area between the impregnated electrode, which is the main body of the electrode, and the high melting point metal rod is small, and the impregnated electrode The heat transfer efficiency between the metal and the high melting point metal is remarkably low. Therefore, heat generated in the impregnated electrode cannot be efficiently dissipated. In order to solve such a problem, an end face having a convex portion is provided on a base portion of the electrode, and the convex portion is inserted into an insertion hole of a main portion of the electrode, and a contact area between the base portion and the main portion of the electrode is provided. An electrode that increases the heat dissipation efficiency by increasing the size of the electrode can be considered.

However, even in the above electrode, there is a slight gap between the base part and the main part of the electrode. The heat dissipation efficiency is not sufficient. If such a gap is formed, the (easily) electron-emitting substance remaining in the gap evaporates as the temperature rises when the discharge tube is used, and adheres to the wall surface of the discharge tube. As a result, the output light quantity of the discharge tube is reduced, and the life of the discharge tube is shortened.

Therefore, an object of the present invention is to solve the above problems and provide a discharge tube having a high heat radiation efficiency and a long life, and a discharge tube electrode used for the discharge tube.

In order to solve the above problems, the discharge tube electrode of the present invention is used for a discharge tube in which a cathode and an anode are opposed to each other and sealed in a discharge gas atmosphere, and an arc discharge is performed between the cathode and the anode. An electrode for a discharge tube, which is formed of a high melting point metal and has an end surface with a convex portion; and a high melting point metal containing an electron-emitting material and having a sharp end at one end. A main body having an end face formed with an insertion hole for inserting a projection of the base at the other end, wherein a gap between the end face of the base and the end face of the main body is closed with a brazing material. Features.

By inserting the protrusion of the base into the insertion hole of the main body, the end face of the base having the protrusion and the end of the main body having the insertion hole are opposed to each other. Here, by closing the gap between the end face of the base portion and the end face of the main body portion with a brazing material, the heat transfer efficiency between the main body portion and the base portion is improved. Further, by closing the gap between the end face of the base portion and the end face of the main body portion with a brazing material, it is possible to prevent the electron-emitting substance from entering the gap from the outside and to prevent the electron-emitting material from entering the gap from the main body portion. Even if the electron-emitting material leaks out, the electron-emitting material is prevented from going outside from the gap.

In the discharge tube electrode of the present invention, the brazing material may be filled in the gap.

By filling the gap with the brazing material, the heat transfer efficiency between the main body portion and the base portion is further improved through the brazing material.

In the discharge tube electrode according to the present invention, the end face of the base portion is larger than the end face of the main body portion. By making the end face of the base portion larger than the end face of the main body portion, the heat radiation efficiency of the main body portion is improved.

In the discharge tube electrode of the present invention, the brazing material may be provided so as to extend from the gap to the side surface of the main body.

Since the brazing material is provided to extend from the gap to the side surface of the main body, the electron-emitting material leaking out from the side surface of the main body is prevented from going outside.

Further, in the discharge tube electrode of the present invention, the main body may be made of an impregnated metal in which a porous high melting point metal is impregnated with an electron emitting material.

By making the main body part an impregnated metal in which a porous high melting point metal is impregnated with an electron easy emitting substance, the electron easy emitting substance is uniformly contained in the main body part and the output light is evenly distributed. The nature increases. In addition, when the main body contains the electron-emitting material by impregnation, the electron-emitting material is usually impregnated after the projection of the base is inserted into the insertion hole of the main body. Since the gap between the end face and the end face of the main body is closed with the brazing filler metal, even when impregnated with the electron-emitting material, the electron-emitting substance is prevented from entering the gap.

Further, in the discharge tube electrode of the present invention, the brazing material has a melting point lower than the melting point of each of the main body and the base and higher than the impregnation temperature at which the main body is impregnated with the electron emitting material. It may be made of a material.

By using a brazing material having a melting point lower than any of the melting points of the main body and the base, the shapes of the main body and the base are secured even when the brazing material is heated and melted to close the gap. . In addition, by using a brazing material having a melting point higher than the impregnation temperature, the brazing material does not evaporate or deform during the impregnation.

The discharge tube electrode of the present invention may be characterized in that the brazing material is a molybdenum-ruthenium brazing material.

The discharge tube electrode of the present invention may be characterized in that the electron-emitting material is formed of a simple substance or an oxide of an alkaline earth metal. By using a simple substance or oxide of alkaline earth metal as the electron-emitting material, the work function of the main body can be effectively reduced.

Further, the discharge tube electrode of the present invention may be characterized in that the tip of the cusp of the main body is exposed, and a coating made of a high melting point metal is provided on the surface of the main body.

By providing such a coating, it is possible to more effectively prevent the emissive radioactive substance oozing out from the side surface of the main body from evaporating to the outside.

In order to solve the above problems, a discharge tube according to the present invention is a discharge tube in which a cathode and an anode are opposed to each other and sealed in a discharge gas atmosphere, and an arc discharge is performed between the cathode and the anode. At least one of the cathode and the anode is any one of the discharge tube electrodes described above.

The use of any one of the above electrodes prevents an electron-emitting substance from entering the gap between the end face of the base portion and the end face of the main body portion from the outside, and also allows the electron-emitting material to enter the gap from the main body portion into the gap. Even if the radiated material exudes, such an electron-emitting material is prevented from going outside through the gap. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view of a discharge tube.

FIG. 2 is a sectional view of the electrode.

FIG. 3A, FIG. 3B, FIG. 3C, and FIG.

FIG. 4 is a graph showing the change over time of the output of the discharge tube.

FIG. 5 is a sectional view of the electrode.

FIG. 6 is a sectional view of the electrode. BEST MODE FOR CARRYING OUT THE INVENTION

A discharge tube according to an embodiment of the present invention will be described with reference to the drawings. The book The discharge tube electrode according to the embodiment of the present invention is included in the discharge tube according to the present embodiment. First, the configuration of the discharge tube according to the present embodiment will be described. FIG. 1 is a sectional view of a discharge tube according to the present embodiment. The discharge tube 10 according to the present embodiment includes a glass bulb 12, a cathode 14, and an anode 16.

The glass bulb 12 is made of quartz and has a substantially rod shape. A hollow gas filling part 12a is formed in the middle part of the glass valve 12, and a discharge gas such as xenon is filled in the inside. A cathode 14 and an anode 16 are arranged inside the gas filled portion 12a so as to face each other. The cathode 14 and the anode 16 are electrically connected to external terminals 18 and 20 provided at both ends of the glass bulb 12, respectively. By applying a voltage between the cathode 14 and the anode 16 via the external terminals 18 and 20, an arc discharge occurs between the cathode 14 and the anode 16, and light is not emitted. It is.

FIG. 2 is a cross-sectional view of a cathode 14 which is one electrode. The cathode 14 includes a cathode tip 22 (main body) and a lead rod 24 (base). The lead rod 24 is formed of molybdenum (a high melting point metal) and has a shape extending in a columnar shape. Here, a columnar projection 24 b is formed on one end surface 24 a of the lead rod 24.

The cathode tip 22 is formed by impregnating porous tungsten (high melting point metal) with barium ((easy) electron-emitting substance). By impregnating barium, which is an alkaline earth metal, the work function of the cathode tip 22 can be reduced, and electrons can be easily emitted. In addition, the cathode tip 22 has a conical point 22 a provided on one end facing the anode 16 and a cylindrical base 22 b provided on the other end. And a shell shape consisting of Here, in particular, a cylindrical insertion hole 22 d into which the projection 24 b of the lead rod 24 is inserted is formed in the end face 22 c of the base 22 b.

The projection 24 b of the lead rod 24 is inserted into the insertion hole 2 d of the cathode tip 22. That is, the end face 24 a of the lead rod 24 faces the end face 22 c of the cathode tip 22. Here, particularly, the end face 24 a of the lead rod 24 is larger than the end face 22 c of the cathode tip 22. Also, the outer diameter of the projection 24 b of the lead rod 24 is substantially the same as the inner diameter of the insertion hole 22 d of the cathode tip 22, and the projection 24 b of the lead rod 24 is connected to the cathode. The lead rod 24 and the cathode tip 22 are joined by press-fitting into the insertion hole 22 d of the tip 22.

The gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 is closed by a molybdenum ruthenium brazing material 26 to isolate the gap from the outside. More specifically, the gap is filled with molybdenum-ruthenium brazing material 26, and the molybdenum-ruthenium brazing material 26 is the end face 2 of the cathode tip 2 2 of the end face 24 a of the lead rod 24. It is provided so as to extend to the portion not facing 2 c and to the side surface of the cathode tip 22. In particular, the melting point of molybdenum-ruthenium brazing material 26 is 195 °, and the melting point (3410 ° C) of evening stainless steel, which is the material of cathode tip 22, and lead rod 2 The melting point of molybdenum, which is the material of item 4, is lower than the melting point (2620 ° C), and it is higher than the impregnation temperature (about 1500 ° C) for impregnating the cathode tip 22 with barium. I have.

The anode 16 is formed of tungsten, and as shown in FIG. 1, a frustoconical tip provided on one end side facing the cathode 14 is connected to a columnar base. It has a shape.

Subsequently, a method for manufacturing the cathode 14 which is one characteristic part of the discharge tube according to the present embodiment will be described. 3A to 3D are manufacturing process diagrams of the cathode 14. To manufacture the cathode 14, first, as shown in FIG. 3A, the projection 24 b formed on the end surface 24 a of the lead rod 24 is formed on the end surface 22 c of the cathode tip 22. Press into the inserted hole 2 2 d.

Thereafter, as shown in FIG. 3B, a tube-shaped molybdenum-ruthenium brazing material 26 is attached to the outer periphery of the base 22 b of the cathode tip 22 and the end surface 24 a of the lead rod 24. Arrange them so that they touch both sides.

Thereafter, when the molybdenum-ruthenium brazing material 26 is heated, as shown in FIG. 3C, molybdenum-ruthenium braze is formed in the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22. The brazing material 26 is filled. Here, by appropriately adjusting the amount of molybdenum-ruthenium brazing material 26, the molybdenum-ruthenium brazing material 26 can be used to convert the molybdenum-ruthenium brazing material 26 to the end face 2 2 of the cathode tip 2 2 of the end face 24 a of the lead rod 24. It can be provided so as to extend to the portion not facing c and to the side surface of the cathode tip 22. In addition, since the melting point of the material constituting the cathode tip 22 and the lead rod 24 is higher than the melting point of the molybdenum-tinium brazing material 26, the cathode for heating and melting the molybdenum-ruthenium brazing material 26 is used. The tip 22 and the lead rod 24 are prevented from being thermally deformed.

Then, as shown in FIG. 3D, the cathode tip 22 is impregnated with barium 28 in an atmosphere of about 150 ° C. Here, since the melting point of the molybdenum-ruthenium brazing material 26 is higher than the impregnation temperature, the molybdenum-ruthenium brazing material 26 is prevented from being evaporated or deformed during the impregnation of the barrier 28. In addition, since barium 288, which is an electron-emitting material, is contained in the cathode tip 22 by impregnation, barium 288 is uniformly contained in the cathode tip 22. Increase.

Next, the operation and effects of the discharge tube according to the present embodiment will be described. In the discharge tube 10 according to the present embodiment, in the cathode 14, the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 is formed by molybdenum-ruthenium brazing material 26. In particular, the gap is closed by filling the gap with a molybdenum-ruthenium brazing material 26. Therefore, entry of an electron-emitting material such as barium from the outside into the gap is prevented. Therefore, when the discharge tube 10 is used, even if the ambient temperature increases, the electron-emitting material does not evaporate and adhere to the wall surface of the discharge tube 10. As a result, the output light quantity of the discharge tube 10 can be maintained satisfactorily for a long time. Thus, the life of the discharge tube 10 can be extended.

The discharge tube 10 according to the present embodiment further includes a molybdenum-ruthenium brazing material 26, a portion of the end surface 24 a of the lead rod 24 that does not face the end surface 22 c of the cathode tip 22, and a cathode. It is provided so as to extend to the side surface of the tip portion 22. Therefore, even if the electron-emitting material leaks out from the side surface of the base 22 b of the cathode tip 22, the electron-emitting material is prevented from going outside. As a result, the life of the discharge tube can be further extended.

FIG. 4 is a graph showing the change over time of the output of the discharge tube 10 (A in FIG. 4) according to the present embodiment and the discharge tube (B in FIG. 4) of the comparative object. Here, the discharge tube according to the comparative object refers to a discharge tube having a cathode that is not filled with a molybdenum-ruthenium brazing material in a gap between an end face of a lead rod and an end face of a cathode tip. As apparent from FIG. 4, the discharge tube according to the present embodiment has a light output that is reduced to about 70% of the initial value when operated for 100 hours, whereas the discharge tube according to the present embodiment has a light output of approximately 70%. A value of 0 can maintain an initial light output of 80% or more even after operation for 100 hours.

Further, in the discharge tube 10 according to the present embodiment, the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 is closed with a molybdenum-ruthenium brazing material 26. By filling the gap with the molybdenum-ruthenium brazing material 26, the heat transfer efficiency between the cathode tip 22 and the lead rod 24 via the molybdenum-ruthenium brazing material 26 is improved. As a result, the heat generated at the cathode tip 22 can be effectively released to the lead rod 24, and the temperature rise of the discharge tube 10 can be effectively prevented. In addition, the discharge tube 10 according to the present embodiment is particularly configured such that the end face 24 a of the lead rod 24 is made larger than the end face 22 c of the cathode tip 22, so that the heat dissipation of the cathode tip 22 is made possible. Improving efficiency.

In addition, in the discharge tube 10 according to the present embodiment, the end face 24 a of the lead rod 24 and the end face 22 of the cathode tip 22 before impregnating the cathode tip 22 with the electron-emitting material. By closing the gap with c with the molybdenum-ruthenium brazing material 26, entry of the electron-emitting substance into the gap is prevented. As a result, it is possible to reduce the amount of the electron-emitting material.

Further, the discharge tube 10 according to the present embodiment is obtained by filling the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 with molybdenum-ruthenium brazing material 26. In addition, it is possible to prevent a variation in heat radiation efficiency between rods, and to manufacture a discharge tube having uniform performance.

The cathode of the discharge tube 10 according to the above embodiment may be a cathode 30 as shown in FIG. That is, while the lead rod 24 of the cathode 14 according to the above embodiment had a cylindrical shape, the lead rod 32 used for the cathode 30 was attached to the end face 22 c of the cathode tip 22. Opposingly, it has a larger end face 32a, and its rear end is shaped like a rod with a small diameter. Even with such a shape of the lead rod 32, the heat transfer efficiency between the cathode tip 22 and the lead rod 32 can be improved, and the temperature rise of the discharge tube 10 can be effectively prevented. Becomes

The cathode of the discharge tube 10 according to the above embodiment may be a cathode 34 as shown in FIG. That is, as compared with the cathode 14, the cathode 34 exposes the tip of the tip 22 a of the cathode tip 22, and also covers the surface of the cathode tip 22 (a high melting point metal). ) Is further provided. After depositing about 200 A of iridium on the surface of the cathode tip 22 by a CVD method, a sputtering method, or the like, the metal coating 36 is applied to the tip of the tip 22 a of the cathode tip 22. It can be easily obtained by removing the located metal film 36 by polishing treatment with a sandpaper, abrasion treatment with a laser beam, or the like. The provision of the metal coating 36 makes it possible to more effectively prevent the evaporation of the electron-emitting substance that has oozed from the side surface of the cathode tip 22. In addition, by providing the metal coating 36 so as to cover a wide area in contact with the lead rod 24, the efficiency of heat transfer from the cathode tip 22 to the lead rod 24 is improved, and the temperature of the discharge tube 10 is increased. The rise can be effectively prevented. In the discharge tube 10 according to the above embodiment, the cathode tip 22 is made of molybdenum and the lead bar 24 is made of molybdenum. Alternatively, rhenium, tungsten, or the like may be used. Further, the material forming the cathode tip 22 and the material forming the lead rod 24 may be the same or different.

Further, in the discharge tube 10 according to the above-described embodiment, although aluminum is used as the electron-emitting material, other elements such as calcium, strontium or other alkaline earth metals or oxides thereof may also be used. May be used. Further, a mixture of two or more of the above simple substances or oxides may be used as the electron emitting material. In addition, in the discharge tube 10 according to the above embodiment, the impregnated cathode tip 22 containing the electron-emitting material by impregnation is used, but this is because of the high melting point metal such as tungsten. A sintered cathode tip in which powder and an electron-emitting material such as barium are simultaneously sintered may be used.

Further, in the discharge tube 10 according to the embodiment, the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 was filled with the molybdenum-ruthenium brazing material 26. However, this can be achieved by closing the gap between the end face 24 a of the lead rod 24 and the end face 22 c of the cathode tip 22 so as to isolate it from the outside. The heat transfer efficiency between the main body and the base is improved by making the end face of the base and the end of the main body opposed to each other and closing the gap with a brazing material. As a result, the radiation efficiency of the discharge tube increases.

In addition, by closing the gap with a brazing material, the electron-emitting material is prevented from entering the gap from the outside, and even if the electron-emitting material leaks into the gap from the main body, such a situation is also prevented. Electron-emissive material is prevented from going out of the gap. Therefore, when the discharge tube is used, even if the ambient temperature rises, the electron-emitting material does not evaporate and adhere to the wall of the discharge tube. As a result, it is possible to maintain the output light quantity of the discharge tube satisfactorily for a long time, and to prolong the life of the discharge tube. You.

In the discharge tube electrode of the present invention, the gap between the main body and the base is filled by filling the gap with a brazing material or making the end of the base larger than the end of the main body. Heat transfer efficiency can be further improved. As a result, heat generated in the main body can be effectively released to the base, and a rise in the temperature of the discharge tube can be effectively prevented.

Furthermore, in the discharge tube electrode of the present invention, the brazing filler metal is provided to extend from the gap to the side surface of the main body, so that the electron-emissive substance that has exuded from the side surface of the main body may be outside. Is prevented. As a result, the life of the discharge tube can be further extended. Industrial applicability

INDUSTRIAL APPLICATION This invention can be utilized for an electrode for discharge tubes, and a discharge tube.

Claims

Scope of word blue

1. A discharge tube electrode used for a discharge tube, which is sealed in a discharge gas atmosphere with a cathode and an anode facing each other and performs arc discharge between the cathode and the anode, formed of a high melting point metal, A base portion having an end surface with a convex portion formed thereon; a high melting point metal formed to contain an electron emitting substance; having a sharp end at one end; and inserting the convex portion of the base portion at the other end. A main body having an end face with an insertion hole formed therein,

An electrode for a discharge tube, wherein a gap between the end face of the base part and the end face of the main body part is closed with a brazing material.

2. The electrode for a discharge tube according to claim 1, wherein the brazing material is filled in the gap.

3. The discharge tube electrode according to claim 1, wherein the end face of the base portion is larger than the end face of the main body portion.

4. The discharge tube electrode according to claim 1, wherein the brazing material extends from the gap to a side surface of the main body.

5. The electrode for a discharge tube according to claim 1, wherein the main body is made of an impregnated metal obtained by impregnating a porous high-melting metal with an electron-emitting substance.

6. The brazing material is made of a material having a melting point lower than the melting points of the main body and the base and higher than an impregnation temperature at which the main body is impregnated with the electron emitting material. The electrode for a discharge tube according to claim 5, wherein

7. The discharge tube electrode according to claim 6, wherein the brazing material is a molybdenum-ruthenium brazing material.

8. The discharge tube electrode according to claim 1, wherein the electron emitting material is formed of a simple substance or an oxide of an alkaline earth metal.

9. While exposing the tip of the cusp of the main body, the front of the main body 2. The electrode for a discharge tube according to claim 1, further comprising a coating made of a high melting point metal covering the surface.

10. A discharge tube in which a cathode and an anode are opposed to each other and sealed in a discharge gas atmosphere, and an arc discharge is performed between the cathode and the anode,

A discharge tube, wherein at least one of the cathode and the anode is the electrode for a discharge tube according to claim 1.